Android example source code file (NoteEditor.java)

This example Android source code file (NoteEditor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

activity, android, content, contentvalues, drawing, edittext, graphics, intent, linededittext, noteeditor, override, paint, projection, rect, state_edit, state_insert, string, ui, uri, view

The NoteEditor.java Android example source code

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.notepad;

import android.app.Activity;
import android.content.ComponentName;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.content.res.Resources;
import android.database.Cursor;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.net.Uri;
import android.os.Bundle;
import android.util.AttributeSet;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.Toast;

import com.example.android.notepad.NotePad.NoteColumns;

/**
 * A generic activity for editing a note in a database.  This can be used
 * either to simply view a note {@link Intent#ACTION_VIEW}, view and edit a note
 * {@link Intent#ACTION_EDIT}, or create a new note {@link Intent#ACTION_INSERT}.  
 */
public class NoteEditor extends Activity {
    private static final String TAG = "NoteEditor";

    /**
     * Standard projection for the interesting columns of a normal note.
     */
    private static final String[] PROJECTION = new String[] {
        NoteColumns._ID, // 0
        NoteColumns.NOTE, // 1
        NoteColumns.TITLE, // 2
    };
    /** The index of the note column */
    private static final int COLUMN_INDEX_NOTE = 1;
    /** The index of the title column */
    private static final int COLUMN_INDEX_TITLE = 2;
    
    // This is our state data that is stored when freezing.
    private static final String ORIGINAL_CONTENT = "origContent";

    // The different distinct states the activity can be run in.
    private static final int STATE_EDIT = 0;
    private static final int STATE_INSERT = 1;

    private int mState;
    private Uri mUri;
    private Cursor mCursor;
    private EditText mText;
    private String mOriginalContent;

    /**
     * A custom EditText that draws lines between each line of text that is displayed.
     */
    public static class LinedEditText extends EditText {
        private Rect mRect;
        private Paint mPaint;

        // we need this constructor for LayoutInflater
        public LinedEditText(Context context, AttributeSet attrs) {
            super(context, attrs);
            
            mRect = new Rect();
            mPaint = new Paint();
            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setColor(0x800000FF);
        }
        
        @Override
        protected void onDraw(Canvas canvas) {
            int count = getLineCount();
            Rect r = mRect;
            Paint paint = mPaint;

            for (int i = 0; i < count; i++) {
                int baseline = getLineBounds(i, r);

                canvas.drawLine(r.left, baseline + 1, r.right, baseline + 1, paint);
            }

            super.onDraw(canvas);
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        final Intent intent = getIntent();

        // Do some setup based on the action being performed.
        final String action = intent.getAction();
        if (Intent.ACTION_EDIT.equals(action)) {
            // Requested to edit: set that state, and the data being edited.
            mState = STATE_EDIT;
            mUri = intent.getData();
        } else if (Intent.ACTION_INSERT.equals(action)) {
            // Requested to insert: set that state, and create a new entry
            // in the container.
            mState = STATE_INSERT;
            mUri = getContentResolver().insert(intent.getData(), null);

            // If we were unable to create a new note, then just finish
            // this activity.  A RESULT_CANCELED will be sent back to the
            // original activity if they requested a result.
            if (mUri == null) {
                Log.e(TAG, "Failed to insert new note into " + getIntent().getData());
                finish();
                return;
            }

            // The new entry was created, so assume all will end well and
            // set the result to be returned.
            setResult(RESULT_OK, (new Intent()).setAction(mUri.toString()));

        } else {
            // Whoops, unknown action!  Bail.
            Log.e(TAG, "Unknown action, exiting");
            finish();
            return;
        }

        // Set the layout for this activity.  You can find it in res/layout/note_editor.xml
        setContentView(R.layout.note_editor);
        
        // The text view for our note, identified by its ID in the XML file.
        mText = (EditText) findViewById(R.id.note);

        // Get the note!
        mCursor = managedQuery(mUri, PROJECTION, null, null, null);

        // If an instance of this activity had previously stopped, we can
        // get the original text it started with.
        if (savedInstanceState != null) {
            mOriginalContent = savedInstanceState.getString(ORIGINAL_CONTENT);
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        // If we didn't have any trouble retrieving the data, it is now
        // time to get at the stuff.
        if (mCursor != null) {
            // Requery in case something changed while paused (such as the title)
            mCursor.requery();
            // Make sure we are at the one and only row in the cursor.
            mCursor.moveToFirst();

            // Modify our overall title depending on the mode we are running in.
            if (mState == STATE_EDIT) {
                // Set the title of the Activity to include the note title
                String title = mCursor.getString(COLUMN_INDEX_TITLE);
                Resources res = getResources();
                String text = String.format(res.getString(R.string.title_edit), title);
                setTitle(text);
            } else if (mState == STATE_INSERT) {
                setTitle(getText(R.string.title_create));
            }

            // This is a little tricky: we may be resumed after previously being
            // paused/stopped.  We want to put the new text in the text view,
            // but leave the user where they were (retain the cursor position
            // etc).  This version of setText does that for us.
            String note = mCursor.getString(COLUMN_INDEX_NOTE);
            mText.setTextKeepState(note);
            
            // If we hadn't previously retrieved the original text, do so
            // now.  This allows the user to revert their changes.
            if (mOriginalContent == null) {
                mOriginalContent = note;
            }

        } else {
            setTitle(getText(R.string.error_title));
            mText.setText(getText(R.string.error_message));
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        // Save away the original text, so we still have it if the activity
        // needs to be killed while paused.
        outState.putString(ORIGINAL_CONTENT, mOriginalContent);
    }

    @Override
    protected void onPause() {
        super.onPause();
        // The user is going somewhere, so make sure changes are saved

        String text = mText.getText().toString();
        int length = text.length();

        // If this activity is finished, and there is no text, then we
        // simply delete the note entry.
        // Note that we do this both for editing and inserting...  it
        // would be reasonable to only do it when inserting.
        if (isFinishing() && (length == 0) && mCursor != null) {
            setResult(RESULT_CANCELED);
            deleteNote();
        } else {
            saveNote();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate menu from XML resource
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.editor_options_menu, menu);

        // Append to the
        // menu items for any other activities that can do stuff with it
        // as well.  This does a query on the system for any activities that
        // implement the ALTERNATIVE_ACTION for our data, adding a menu item
        // for each one that is found.
        Intent intent = new Intent(null, getIntent().getData());
        intent.addCategory(Intent.CATEGORY_ALTERNATIVE);
        menu.addIntentOptions(Menu.CATEGORY_ALTERNATIVE, 0, 0,
                new ComponentName(this, NoteEditor.class), null, intent, 0, null);

        return super.onCreateOptionsMenu(menu);
    }
    
    

    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        if (mState == STATE_EDIT) {
            menu.setGroupVisible(R.id.menu_group_edit, true);
            menu.setGroupVisible(R.id.menu_group_insert, false);
            
            // Check if note has changed and enable/disable the revert option
            String savedNote = mCursor.getString(COLUMN_INDEX_NOTE);
            String currentNote = mText.getText().toString();
            if (savedNote.equals(currentNote)) {
                menu.findItem(R.id.menu_revert).setEnabled(false);
            } else {
                menu.findItem(R.id.menu_revert).setEnabled(true);
            }
        } else {
            menu.setGroupVisible(R.id.menu_group_edit, false);
            menu.setGroupVisible(R.id.menu_group_insert, true);
        }
        return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle all of the possible menu actions.
        switch (item.getItemId()) {
        case R.id.menu_save:
            saveNote();
            finish();
            break;
        case R.id.menu_delete:
            deleteNote();
            finish();
            break;
        case R.id.menu_revert:
        case R.id.menu_discard:
            cancelNote();
            break;
        }
        return super.onOptionsItemSelected(item);
        
    }
    
    private final void saveNote() {
        // Make sure their current
        // changes are safely saved away in the provider.  We don't need
        // to do this if only editing.
        if (mCursor != null) {
            // Get out updates into the provider.
            ContentValues values = new ContentValues();

            // Bump the modification time to now.
            values.put(NoteColumns.MODIFIED_DATE, System.currentTimeMillis());

            String text = mText.getText().toString();
            int length = text.length();
            // If we are creating a new note, then we want to also create
            // an initial title for it.
            if (mState == STATE_INSERT) {
                if (length == 0) {
                    Toast.makeText(this, R.string.nothing_to_save, Toast.LENGTH_SHORT).show();
                    return;
                }
                String title = text.substring(0, Math.min(30, length));
                if (length > 30) {
                    int lastSpace = title.lastIndexOf(' ');
                    if (lastSpace > 0) {
                        title = title.substring(0, lastSpace);
                    }
                }
                values.put(NoteColumns.TITLE, title);
            }

            // Write our text back into the provider.
            values.put(NoteColumns.NOTE, text);

            // Commit all of our changes to persistent storage. When the update completes
            // the content provider will notify the cursor of the change, which will
            // cause the UI to be updated.
            try {
                getContentResolver().update(mUri, values, null, null);
            } catch (NullPointerException e) {
                Log.e(TAG, e.getMessage());
            }
            
        }
    }

    /**
     * Take care of canceling work on a note.  Deletes the note if we
     * had created it, otherwise reverts to the original text.
     */
    private final void cancelNote() {
        if (mCursor != null) {
            if (mState == STATE_EDIT) {
                // Put the original note text back into the database
                mCursor.close();
                mCursor = null;
                ContentValues values = new ContentValues();
                values.put(NoteColumns.NOTE, mOriginalContent);
                getContentResolver().update(mUri, values, null, null);
            } else if (mState == STATE_INSERT) {
                // We inserted an empty note, make sure to delete it
                deleteNote();
            }
        }
        setResult(RESULT_CANCELED);
        finish();
    }

    /**
     * Take care of deleting a note.  Simply deletes the entry.
     */
    private final void deleteNote() {
        if (mCursor != null) {
            mCursor.close();
            mCursor = null;
            getContentResolver().delete(mUri, null, null);
            mText.setText("");
        }
    }
}